Method of forming single operation rivet

ABSTRACT

THIS DISCLOSURE HAS TO DO WITH A RIVET WHICH IS FORMED FROM SHEET MATERIAL AS AN INTEGRAL COMPONENT THEREOF. THE RIVET DIFFERS FROM OTHER RIVETS IN THAT ALTHOUGH IT IS OF A TUBULAR CONSTRUCTION THE BODY AND CLOSED END THEREOF HAVE THE MATERIAL THEREOF COMPRESSIVELY STRESSED. THE RIVET IS FORMED IN A SINGLE OPERATION THROUGH THE EXTRUSION FLOW OF THE MATERIAL OF THE SHEET BETWEEN A PAIR OF PUNCHES AND AS A PART OF THE OPERATION, THE RIVET MAY ALSO BE HEADED. THE RIVET IS READILY FORMED UTILZING A TOOL SET CONSISTING SOLELY OF TWO OPPOSED MALE PUNCHES AND HAS PARTICULAR ADAPTABILITY TO THE SECUREMENT OF PULL TABS TO EASY OPENING CONTAINER ENDS.

Jan. 26, 1971 R, B K ETAL 3,557,441

METHOD OF FORMING SINGLE OPERATION RIVET Filed Jan. 5, 1968 w x j $16.4

'1 a 25 fill/11 INVENTORS ARNOLD R. BO\K 6n ALBERT J. HOLK ,Jr.

United States Patent US. Cl. 29--509 4 Claims ABSTRACT OF THE DISCLOSURE This disclosure has to do with a rivet which is formed from sheet material as an integral component thereof. The rivet differs from other rivets in that although it is of a tubular construction the body and closed end thereof have the material thereof compressively stressed. The rivet is formed in a single operation through the extrusion flow of the material of the sheet between a pair of punches and as a part of the operation, the rivet may also be headed. The rivet is readily formed utilizing a tool set consisting solely of two opposed male punches and has particular adaptability to the securement of pull tabs to easy opening container ends.

This invention relates in general to new and useful improvements in rivet construction and method of forming rivets, and more particularly to a rivet which is formed out of an integral width sheet material.

A primary feature of this invention is the ability to form a rivet from sheet material as an integral component of such sheet material with the rivet being formed in a single operation and wherein the single operation is also capable of heading the rivet.

Another feature of this invention is the provision of a simple tool set particularly adapted to form in a single operation a rivet from an integral width sheet material, the tool set including a pair of opposed punches of which one punch is of a smaller section than the other and the section of the smaller punch corresponding to the section of the desired rivet.

Another feature of this invention is the provision of a rivet which is integrally formed with and out of sheet material and wherein the material of the rivet is compressively stressed.

A further object of this invention is to provide a novel rivet which may be formed in a single operation and which rivet may be utilized to secure an apertured member to sheet material merely by placing the apertured member on the sheet material and positioning the apertured member and sheet material in alignment between a pair of opposed male punches, followed by the movement of the punches together so as to effect the extrusion of the sheet material in a manner to form a rivet passing through the aperture of the apertured member and headed over so as to secure the apertured member to the sheet material.

A specific feature of this invention is the adaptability of the rivet and the method of forming the same to the securement of pull tabs to easy opening container ends.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the several views illustrated in the accompanying drawing.

In the drawing:

FIG. 1 is a schematic elevational view of a tool set showing the initial relationship of the tool set with respect to sheet material from which a rivet is to be formed.

FIG. 2 is an elevational view similar to FIG. 1 and shows the relationship of the punches after the desired ice rivet has been formed therewith, the sheet material being shown in cross section.

FIGS. 3 through 6, inclusive, are views similar to FIG. 1 showing schematically the steps of forming in a single operation a rivet and the utilization of such a rivet to secure an apertured member to a sheet from which the rivet is formed.

FIG. 7 is an enlarged fragmentary sectional view taken through a portion of a rivet formed in accordance with this invention and shows schematically the compressive material flow therein.

FIG. 8 is a top perspective view of a can end having a pull tab secured thereto by means of an integral rivet formed in accordance with this invention.

Referring now to the drawings in detail, it will be seen that there is illustrated in FIGS. 1 and 2 the manner in which a rivet is formed in a single operation in accordance with this invention. In accordance with this invention, a rivet is formed in and of sheet material in a single operation utilizing an extremely simple tool set which is generally referred to by the numeral 10. The tool set 10 includes a pair of male punches which are disposed in opposed relation, the male punches including punches 11 and 12. It is to be noted that the punch 12 is of a smaller cross section than the punch 11. It is further to be noted that the section of the punch 12 corresponds to the intended internal section of the rivet to be formed.

In the schematic showing of FIGS. 1 and 2, the punch 12 is illustrated as being stationary and the punch 11 as being movable towards the punch 12. It is to be understood, however, that all that is required is that there is relative movement of the punches 11 and 12 so that sheet material, such as the sheet 13 positioned between the punches 11 and 12 will be compressively stressed. It is also necessary that the section of the punch 11 at least be greater than the external section of the rivet to be formed.

In accordance with the principles of this invention, as the punches 11 and 12 are brought together with the sheet 13 clamped therebetween, that portion of the sheet 13 which is disposed between the opposed faces of the punches 11 and 12 is compressed and since the material of the sheet 13 is flowable under pressure. there is radial flow or extrusion of the compressed metal. It has been found that the resistance of the sheet 13 to enlargement due to radial flow of the compressed material thereof results in the radially flowing material to change its direction outside of the punch 12 to axial flow. As a result, the material of the sheet 13 immediately surrounding the punch 12 begins to flow axially around the punch 12. This results in the movement of the entire sheet 13 axially surrounding the punch 12 so that a rivet is formed, as is shown in FIG. 2.

The rivet, which is generally referred to by the numeral 4, includes a tubular body 15 which snugly surround the punch 12 and thus has an internal section corresponding to that of the punch 12. In addition, the rivet 14 includes a closed end 16 which is spaced from the sheet 13. The open end of the rivet 14 is, of course, integrally connected to the sheet 13.

Reference is now made to FIG. 8 wherein there is illustrated a container end which is in the form of an easy opening can end generally referred to by the numeral 17. The can end 17 includes an end panel 18, which is formed of sheet material. and to which there is secured a pull tab 20. The pull tab 20 is permanently secured to the end panel 18 by means of an integrally formed rivet 21.

Referring now to FIGS. 3 through 6, it will be seen that employing the rivet forming principles of FIGS. 1 and 2 and utilizing a particularly conformed tool set, which is generally referred to by the numeral 22, in a single operation the pull tab 20 may be secured to the end panel 18 by the formation and heading of the rivet 21. The tool set 22 includes a pair of opposed male punches which 3 includes a larger cross section punch 23, and a smaller cross section punch 24. The punches 23 and 24 correspond to the punches 11 and 12, respectively.

It is to be noted that the punch 24 is of a section corresponding to the internal section of the intended rivet. It is also to be noted that the punch 24 is a projecting portion of a larger punch member 25 and there is a shoulder 26 surrounding the punch 24. The axial extent of the punch 25 corresponds to the desired internal axial extent of the rivet 21.

The shoulder 26 is of a sufficient radial extent to provide for an adequate supporting of the end panel 18 during the formation of the rivet 21. At the same time, the cross section of the punch 23 is such as to extend radially beyond any portion of the formed rivet and at the same time small enough to be received within an associate portion of the pull tab 20. At this time, it is pointed out that the pull tab 20 has a pre-formed aperture 27 therein.

Referring now to FIG. 3 in particular, it is to be noted that the end panel 18 is positioned on the punch 24 in the desired relation relative thereto. Also, the pull tab 20 is positioned on the end panel 18 in the desired relative position. The pull tab 20 has the apertures 27 thereof in alignment with the punches 23 and 24.

When the end panel 18 and the pull tab 20 are properly positioned relative to the punches 23 and 24, the punches are brought together. It will be readily apparent that the punch 23 initially engages the pull tab 20 with the result that the punch 24 serves to force the metal of the end panel 18 up into the aperture 27 until such metal engages the face of the punch 23, as is shown in FIG. 4. When this occurs, there is a slight flexing of the end panel 18 and the portion of the pull tab 20 surrounding the aperture 27. However, this fiexure is not permanent in nature.

As the material of the end panel 18 aligned with the aperture 27 becomes tightly clamped between the faces of the punches 23 and 24, there is initial radial flow of the type described with respect to FIGS. 1 and 2, followed by axial flow of such material. In this manner, the rivet 21 is formed in a single operation from the material of the end panel 18 and through the aperture 27 in the pull tab 20. Furthermore, that portion of the pull tab 20 defining the aperture 27 functions as a die for the extrusion of the rivet 21 therethrough so that there is a very tight fit between the rivet 21 and the pull tab 20.

The extrusion of the material of the end panel 18 continues until the end panel 18 comes to rest on the shoulder 26, as is illustrated in FIG. 5. At this time the rivet forming is complete. The rivet 21 at this time includes a tubular body 28, which is integrally connected at its open end to the end panel 18, and a transverse closed end 29, which is disposed above the plane of the surrounding surface of the pull tab 20.

Referring now to FIG. 6, it will be seen that further movement of the punches 23 and 24 together results in a radial extrusion of the closed end 29 outwardly beyond the tubular body 28 so as to form a head or shoulder 30 on the rivet 21 which secures the pull tab 20 on the rivet 21 and in clamped engagement against the surface of the end panel 18.

It thus will be readily apparent from the foregoing that not only is the rivet 21 formed in a single operation, but as a part of that single operation, the rivet is also headed.

Reference is now made to FIG. 7 in particular wherein there is illustrated an enlarged section through the rivet 14. It is to be understood that inasmuch as the entire rivet 14 is formed by the flowing of the material of the sheet 13 under compression, the entire rivet 14 is in compression. The material of the closed end 16 of the rivet 14 has flowed radially and is compressed both radially and axially. The material of the tubular body 15 of the rivet 14 has flowed axially only and is, of course, compressed axially due to the method of forming the rivet. Thus, the rivet 14 differs from conventional rivets which are punched from sheet material in that where the material of such rivets is in tension, the material of the rivet 14 is in compression.

At this time it is pointed out that the materials of the sheets from which rivets may be formed in accordance with this invention are preferably readily flowable soft metals, such as aluminum. However, the invention is not so restricted and it is feasible to form rivets in accordance with this invention from steel sheets and such harder metals, as well as plastic sheets.

It is also pointed out at this time that although it is preferred that the rivets formed in accordance with this invention be headed in the course of the single operation of forming, it is feasible to separately form the rivet in the manner illustrated in FIGS. 1 and 2, position the pull tab 20 over the rivet, and thereafter head the rivet. Furthermore, the rivet may initially be of sufficient axial extent whereby the heading thereof may be in the form of a crimping or upsetting operation as opposed to the radial extrusion type flow illustrated in FIG. 6.

Although only a preferred embodiment of the invention has been specifically illustrated and described herein, it is to be understood that minor variations may be made in the rivet configuration, construction and method of forming the same, without departing from the spirit and scope of the invention, as defined by the appended claims.

We claim:

1. A single operation method of forming a rivet on a first sheet material member formed of a material that is flowable under pressure and passing the rivet through an aperture in a second sheet material member for securing the members together comprising the steps of providing a pair of male punches disposed in opposed aligned relation with one of the punches being of a smaller section than the other and of a section in accordance with the section of the intended rivet, placing the members between the punches with the second member aperture aligned with the punches and the second member being between the first member and the other punch, and moving the punches together to thereby clamp the first member therebetween under sufficient pressure to effect extrusion of the material of the first member with the extruded material flowing longitudinally around the smaller punch and through the apertured second member under the control of the apertured second member.

2. The method of claim 1 wherein the longitudinal flow of the sheet material is limited by a stop shoulder on the smaller punch and after which there is further movement of the punches together effecting a transverse flow of the sheet material to form a head on the rivet remote from the smaller punch.

3. The method of claim 2 wherein the forming of the rivet head is between and controlled by the other punch and the apertured second member.

4. The method of claim 1 wherein said method is particularly adapted to the securement of a pull tab to an easy opening container end and wherein the first sheet material member is in the form of a container end and the second member is in the form of an apertured pull tab, and wherein the other punch initially engages only the pull tab and initial material How is through the pull tab into engagement with the other punch.

References Cited UNITED STATES PATENTS 1,802,843 4/1931 Singer 72-377X 3,031,748 5/1962 Focht 113116(FF)X 3,357,388 12/1967 Dunn 113-121(C) 3,359,935 12/ 1967 Rosbottom 29-509X 3,387,481 6/1968 Harvey et al 72-377X CHARLIE T. MOON, Primary Examiner U.S. C1. X.R. 

